Catalyzed halogenation of rubbery copolymers



2,948,709 I Pa ed Ag 9, 19

2,948,709 CATALYZED HALOGENATION 0F RUBBERY COPOLYMERS Irving Kuntz, Roselle Park, N.J., assignor to Esso Research and Engneering Company, a corporation of Delaware No Drawing. Filed 101%-27, 1956-, Ser. No. 630,770

Claims". (G1. loll-85.3)

This invention relates to rubbery polymeric compositions which are halogenated low unsaturation hydrocarhon materials and particularly. copolymers of isoolefins andf multiolefins and to the preparation of such compositions. More particularly thepresent'ihvention relates to improved methods for halogenating'butyl' rubber at low temperatures and at a rapid rate with minor proportions of certain N-halogeno compounds in the presence of minor proportions of'peroxide catalysts.

Butyl rubber is a copolymer of a major proportion of a C to C isoolefin and a minor proportion of a C to C multiolefin. These. copolymers are commonly referred to in the literature as butyl rubber or GR-I rubber (Government Rubber-Iso'butylene) and for example, is referred to as butyl rubber in the book"Synthetic Rubber by'G. S. Whitby. The expression buty'lrubber-"as employed in the specification and claims is intended to include copolymers. containing about 85 to 99.5"weight percent of anisoolefin and about 15 to 0:5 weight percent of a multi olefin which is preferably a conjugated diolefin. The'preparatiofnv of butyl rubbenwhich is preferably the reaction product of isobutyleneand isoprene, is'amply described in [1.8. Patent No. 2,356,128 toThomaset al.

Butyl'rubb'ermay beim'proved as to covulcanizability with other rubbery polymers and particularly with high unsaturation rubbers such as diene rubbers or natural rubber by. partially halogenating the butyl rubber at elevat'ed temperatures of say at least about 80 to 120 C. with solid v halogenated agents of'the classof- N-b'romo or N-chloroorganic compounds. In order for-"such halogenations to be. performed at relatively fast rates the foregoing temperatures are the minimum useable. However, such a process results in molecular weight breakdown of the butyl'rubber copolymer during :halogenation. It has been attempted to halogenate butyl rubber with.- N-halogeno compounds at temperatures ofless'th'an about 80 C. but such low temperatures result inaninferior product. For instance, such rubbers have not been found to be covulcanizable. with high unsaturation-rubbery polymers such as naturalrubber, diene-styrene, co-

polymers, diene nitrile rubbers, chloroprene rubber of the like and cannot be cured satisfactorily solely with basic metal compounds such as zinc stearate or especially zinc oxide.

In accordance'with the present invention, it has now been discovered that when butyl rubber is reacted with N-halogeno'bompounds in the presence of about 0.01 to 25 weight percent, preferably between about0.05 to'20 weight percent and even more especially about 0.1 to 15 weight percent based -on-rubber of a peroxide catalyst,

high quality partially halogenated derivatives of butyl rubber are:produce at temperatures-belowabout-75 C.

The halogenated butyl rubbers produced accordance in admixture with carbon blackswwith orwithout'such 'copolym e'rs produced in accordance with the present in vention have alsobeen found to be readily cowlcanizable with other rubbery polymers such as those hereinbefore mentioned to produce vulca nizates having satisfactory tensile strengths of well above 1,000 p.s.i. and in many cases' above 2,000 psi i I In a preferred embodiment of the present invention, butyl" rubber is dissolved in an inert solvent and halogenated' by N-halo geno compounds in the presence of the above mentioned amounts of a peroxide catalyst at temperatures below about C., advantageously between about 10 to 70 C. and preferably between about2.0 to 60 C. for times between about 1 minute to 5 hours and preferably between about 5 minutesand 2 hours. The rubber solvents employed are those which do not react with peroxide type catalysts or N-halogeno compounds and are, preferably substantially saturated normal aliphatic or aromatic, hydrocarbons and/or halogenated derivatives thereof, examples of which are hexane, heptane, benzene, chlorobenzene, chloroform dichloroethane, carbon tetrachloride, mixtures thereof, etc.

For the purposes of the presentinvention, the peroxide catalyst may comprise-such peroxidic material as hydrogenperoxide, dicumyl peroxide, benzoyl peroxide, tetral in. hydroperoxide, ditertiary butyl peroxide, ascaridole, tertiary butyl hydroperoxide, cumene hydroperoxide, peracetic acid, acetyl peroxide, etc.

TheN-halogeno compounds, useful for; the purposesof the present invention, are preferably N-bromoand/or N-chloro-compounds' examples of which are N,N'-dichloro -5,5 -dimethylhydantoin, N-bromo succinimide, Nlialogeno phthalimides such as N-bromo phthalimide or N chlorophthalirnide, N,N'-dibromo 5,5 dimethyl hydantoin, etc. a

The. foregoing compounds maybe generalized by the formulae:

R/ O (I) and the group consisting of hydrogen, and C to C alkyl,}

aryl',' aralkyl and alkaryl groups, and X is halogen, preferably-chlorine and/or bromine.

' In preparing chlorinated butyl rubber or brominated butyl rubber accordance with the present invention, the rubbery-"copolymer is dissolved so as to form about a2 to 40 rweightprcentsolution in one of the foregoing rubber solvents? The 'resulting'solution is then contacted: with of an N-chloro and/or N-bromo compoundsuch: asthose outlin'ed above, and also with a peroxidecatalystof'the type and in the'amounts inbefore described, at temp'er'atures between about 10 -nation or chlorination conditions but catalyzing the reaction in accordance with the present invention with 1 minor proportions of a peroxide catalyst. Also, the halogenation is carried out so as to make the resulting halogenated butyl rubber contain at least about 0.5 weight percent, preferably at least about 1.0 weight percent halogen but not more than a halogen content of about 3.0 X weight percent and preferably not more than a halogen content of about 2.0 X weight percent wherein:

- and: I

L=mole percent of the mulu'olefin in the polymer M =molecular weight of the isoolefin Restated, the polymer should have a halogen content of at least about 0.5 weight percent, but not more than about 3 atoms of halogen per molecule of multiolefin present in the polymer and preferably not more than about 2 halogen atoms per molecule of multiolefin, i.e. not more than about two atoms of halogen per double bond in the copolymer. Based on the above, the amount of N-halogenocompound employed is generally between about 1.0 and 80 weight percent and preferably between about 5.0 and 50 weight percent based on butyl rubber. The amount will depend upon the unsaturation of the butyl rubber copolymer as well as the molecular weight of the N-halogeno compound.

The halogenated copolymer formed advantageously has a viscosity average molecular weight of between about 250,000 and 2,000,000 and a mole percent unsaturation of between about 0.2 to 15.0, advantageously about 0.4 to and preferably about 0.6 to 3.0. This copolymer has substantially the same molecular weight as the unhalogenated copolymer and when cured has good to excellent tensile strength, extension modulus, abrasion resistance, elongation, and flexure resistance and outstanding gas impermeability and heat aging properties. The halogenated rubbery copolymer also has the property of being vulcanizable with zinc oxide and/or sulfur with or without other added vulcanization accelerators and is also covulcanizable with other rubbery polymers. The vulcanization of such a copolymer halogenated in accordance with the present invention, is generally performed at temperatures between about 200 and 450 F. preferably between about 250 and 400 F. for times between about a minute up to several hours (e.g. 5.0) or more.

The resulting halogenated butyl rubber, produced in accordance with the present invention, whether chlorinated butyl rubber and/or brominated butyl rubber, may be recovered in generally the same manner as for unmodified butyl rubber. For example, the chlorinated butyl rubber and/or brominated butyl rubber polymer may be recovered from solution by precipitation with acetone or any other known non-solvent for the rubber with a subsequent drying step under about 1 to 760 mm. or higher of mercury pressure absolute at temperatures between about 0 and 180 C., preferably between about 50 and 150 C. (e.g. 70 C.). Other methods of recovering the halogenated butyl rubber copolymer from the solution of the same are by conventional spray or drum drying techniques. Alternatively the halogenated butyl rubber. containing-solution may be injected into a 4 vessel containing a higher boiling polymer non-solvent, preferably agitated water, heated to a temperature sufficient to flash ofl? the solvent and form an aqueous sluny of the halogenated butyl rubber. The rubber may then be recovered from this slurry by filtration, dried and recovered as a crumb or as a dense sheet or slab by conventional milling and/or extruding procedures.

In order to more fully illustrate the present invention, the following experimental data are given:

Example I A solution of a commercial butyl rubber corresponding to GR-Il8 rubber is prepared having a concentration of 70 grams of rubber copolymer dissolved in 700 cc. of benzene. The rubber has a Mooney viscosity at 212 F. for 8 minutes of 75, a mole percent unsaturation of 1.6, and a viscosity average molecular weight of 310,000. To the foregoing solution is then added 18 grams of N,N-dichloro 5,S-dimethyI-hydantoin and to this solution there is added 10 grams of ditertiary butyl peroxide. The reaction solution is then heated at 40- C. (e.g. 50 C.) for 1.5 hours. The chlorinated butyl rubber formed is then isolated by conventional solution-precipitation technique using hexane as the solvent and acetone as the antisolvent. Upon analysis, the rubber is found to contain 1.95 weight percent chlorine and 0.011% nitrogen. The solution of the chlorinated copolymer also has an intrinsic viscosity in diisobutylene of 1.10 and a viscosity average molecular weight of 305,000.

100 parts by weight of the foregoing rubbery chlorinated butyl copolymer are then compounded on a rubber mill into the following formulation:

Components: Parts by weight SRF carbon black (Pelletex) 50 Zinc oxide 5 Stearic acid 0.5

Upon curing the foregoing compounded chlorinated butyl rubber, produced in accordance with the present invention, at a temperature level of 300 F. for a time of 60 minutes, the following physical inspections are noted:

Property: Value Tensile strength (p.s.i.) 1270 Elongation (percent) 390 Extension modulus at 300% elongation (p.s.i.) 950 alyst results in a product which cannot be vulcanized by metal oxides alone.

' Example II The same general procedure as in Example I is repeated using 0.1 gram of benzoyl peroxide as the peroxide catalyst and 30 grams of N-brorno succinimide as the halogenating agent for a reaction period of one hour. The modified butyl rubber formed contains 2.94 weight percent bromine and has an intrinsic viscosity in diisobutylene of 1.11 corresponding to a viscosity average molecular weight of 310,000. Upon compounding and curing in accordance with Example I, the brominated vulcanizate formed is found to have a tensile strength above 1,000 p.s.i., an elongation above 300% and a modulus at 300% elongation between 900 and 1200 p.s.i.

Example II shows, as does Example I, that butyl rubber may be halogenated 'with N-halogeno compounds at temperatures between about 20 and 70' C. in the presence of peroxide catalysts to yield good vulcanizates whereas in all instances where the halogenation is performed in the absence of peroxide catalysts, products which do not vulcanize with metal oxides are obtained.

Resort may be had to various modifications and variations of the disclosed embodiments of the present invention without departing from the spirit of the invention or the scope of the appended claims.

What is claimed is:

1. In a process for halogenating rubbery isoolefinmultiolefin copolymers, the improvement which comprises dissolving the copolymer in an inert solvent, reacting said copolymer with a cyclic N-halogeno compound as the halogenating agent at a temperature level of between about 10 and 75 C. in the presence of about 0.01 to 25 weight percent based on copolymer of a peroxide catalyst, said cyclic N-halogeno compound having a structure selected from the group consisting of:

Oin R. (I)

and

n and m being about 0 to 20, R to R being selected from the group consisting of hydrogen, and C to C alkyl groups, and X being selected from the group consisting of chlorine and bromine, the halogenation reaction being conducted until the copolymer contains at least about 0.5 weight percent combined halogen but not more than 3.0 X weight percent combined halogen in which:

and

=mole percent of the multiolefin in the polymer M =molecular weight of the isoolefin M =molecular weight of the multiolefin M =atomic weight of chlorine or bromine.

2. A process according to claim 1 in which the halogenating agent contains chlorine.

3. A process according to claim 1 in which the halogenating agent contains bromine.

4. A process according to claim 1 in which the copolymer is butyl rubber, the peroxide catalyst being selected from the group consisting of ditertiary butyl peroxide, benzoyl peroxide, dicumyl peroxide, cumene hydroperox ide, and mixtures thereof.

5. A process according to claim 4 in which the butyl rubber is reacted with the N-halogeno compound while the butyl rubber is dissolved in a substantially inert solvent.

6. A prOcess for halogenating an isoolefin-multiolefin butyl rubber copolymer which comprises dissolving the butyl rubber copolymer in a substantially inert solvent,

6 regulating the temperature to a level between about 10 and 70 C. and reacting the butyl rubber copolymer while dissolved in the solvent with a cyclic N-halogeno compound, said cyclic N-halogeno compound having a structure selected from the group consisting of:

and

wherein n and m are 0 to 20, R to R being selected from the group consisting of hydrogen, and C to C alkyl, aryl, aralkyl and alkaryl groups, and X is selected from the group consisting of chlorine and bromine, in the presence of about 0.05 to 20 weight percent based on copolymer of a peroxide catalyst until the copolymer contains at least about 0.5 weight percent combined halogen but not more than about 2.0 X weight percent combined halogen in which:

M L (L) M1+L(M2+ a) X 100 and:

L mole percent of the multiolefin in the polymer M =molecu1ar weight of the isoolefin M =molecu1ar weight of the multiolefin M atomic weight of chlorine or bromine.

References Cited in the file of this patent UNITED STATES PATENTS 2,291,574 Gleason et al. July 28, 1942 2,327,517 Frolich et al. Aug. 24, 1943 2,631,984 Crawford et al. Mar. 17, 1953 2,681,899 Crawford et al. June 22, 1954 2,732,354 Merrissey et al. Jan. 24, 1956 2,779,764 Paterson Jan. 29, 1957 2,804,448 Hallenbeck Aug. 27, 1957 2,816,098 Morrissey Dec. 10, 1957 OTHER REFERENCES Salellas et al.: Chem. Abs., 45, page 2873 (1951). 

1. IN A PROCESS FOR HALOGENATING RUBBERY ISOLEFINMULTIOLEFIN COPOLYMERS, THE IMPROVEMENT WHICH COMPRISES DISSOLVEING THE COPOLYMER IN AN INERT SOLVENT, REACTING SAID COPOLYMER WITH A CYCLIC N-HALOGENO COMPOUND AS THE HALOGENATING AGENT AT A TEMPERATURE LEVEL OF BETWEEN ABOUT 10* AND 75*C. IN THE PRESENCE OF ABOUT 0.01 TO 25 WEIGHT PERCENT BASED ON COPOLYMER OF A PEROXIDE CATALYST, SAID CYCLIC N-HALOGENO COMPOUND HAVING A STRUCTURE SELECTED FROM THE GROUP CONSISTING OF: 